Process for recovering nitrogen compounds



Patented Oct. 21, 1941 PROCESS FOR RECOVERI'N G NITROGEN COMPOUNDS George Ryder Lake, Long Beach, Calif., assignor to Union Oil Company of California, Los

Angeles,.0alif., a-corporationof California No Drawing. Application February 14, 1838, Serial No. 190,4372

2 Claims. ((21. 260E269) to 'a process for organic nitrogen The present invention relates the separation and recovery of bases, and more particularly pertains to the separation and recovery of such nitrogen :bases from by-pro'ducts resulting from the processing of petroleum oils, their fractions and/or distillates, as well as of shale oils, coal tars andproducts obtained by thepyrolysis of such' substances as cottonseed meal.

Although most naphthenic and asphalt base petroleum oils contain varying. amounts of nitrogen compounds or nitrogen bases, attempts to remove them from such crude O11S,'OI' even from their distillates, result in the: extraction of only negligible amounts of such nitrogenous basecompounds. Suchrecovery is highly uneconomical, and it was known for a long .timethat efiicient recovery thereof requires a preliminary concentration ofthe nitrogen .basesin some one fraction. It has also beenpreviouslyfoundthat the sludges resulting from the treatment. f-petroleumand like distillates, and particularlycracked gasoline and kerosene fractions, with heavy metal salts or. with concentrated sulphuric acid, contain a sufficient quantity or concentration of these nitrogenous compounds. to make their recovery therefrom commercially economical.

The nitrogen compounds found in the sludges resulting from theaforementioned acid treatment of petroleum fractions are comparatively easily recoverable from such sludges. This is due to the fact that these nitrogenous compounds are. usually present in such sludges in the form of their simple acid salts. However, the sludges obtained during the treatment of petroleum fractions or distillates with heavy metal salts, as for example with zinc chloride and other metal halides, contain a complex mixture of' various: petroleum and other substances. Thus, besides complex nitrogen-base-metal salts, such sludges also contain non-basic substances of the type of the metal salt used for the petroleum refining, water, phenols, sulphur compounds, low boiling hydrocarbons, and some high boiling inert compounds.

The presence of all these substances in admixture with the nitrogen bases and complex nitrogen base salts, renders the recovery of the nitrogen bases highly diflicult. In fact, when employing the ordinary methods oi acid and alkali extraction, this recovery isifre'quently found to be impossible. Thus, the recovery ofthe nitrogen bases from these sludges produced by treatment of petroleum fractions and/or distillates (as well" as of the other 'enumeratedIsubstances) with heavy-metal salts is complicated by the q necessitates the use of presence 'o'f the above mentionedcomplex basemetal salts. In view of the fact that these complex salts are only partiallyso'luble in dilute acids, therecovery of nitrogen bases from such sludges excess quantities of acids. Also, the recovery of nitrogen bases by thisacidalkali method requires excessive quantities of caustic or alkali toform the soluble metalates, as for example, the soluble zincate, if zinc-chloride is the heavy metal salt employecl'in the original treatment of the petroleum fraction. The use of an insufficient quantity of caustic is found to be detrimental in that' it results in the formation of very stable emulsions which hinder, and even prevent, any economical recovery of nitrogen basesfrom sludges thus emulsified.

It istherefore the main object of the present invention toobviate the above defects existing in the present methods of recovering nitrogen bases from complex sludge mixtures. It is a further object of this invention to provide a simple and economical method for the recovery of nitrogen bases from complex sludge mixtures resulting from the treatment of petroleum, shale oil, coal P tars, etc., with heavy metal salts such as the chlorides of zinc, mercury, cadmium, lead and mercury.

It has now been discovered that the above and other objects maybe realized by subjecting the above' described sludge acids or sludges to one or more extractions with water. It has been further discovered that these water extractions may befollowed by or interspersed with one or more extractionsof the residual sludges with an inorganic-acid, this extraction removing the free bases and/or water insoluble complex base salts crude complex mixture. further stated to reside in'the above water exstill remaining in such slu dges. The extracts recovered by the water and acid extractions may be further'treated either separately or together for the recoveryof' the nitrogen bases. For this purpose the'two extracts, whether separate or combined, are treated by the addition of caustic such "as sodium hydroxide, which causes the cracking out of the bases, and permits their liberation and. separation from the water solution,

the nitrogen bases .being found as the supernatant layer. a

The'invention may thereforebe stated to reside in one or more water treatments of the sludges obtainedfrom the treatment-of petroleum. oilsv or the like, their fractions and/or distillates with heavy metal salts, for the purpose of extracting from such sludges nitrogen'bases present in the The invention may be traction followed by or interspersed with the extraction of the residual sludges with inorganic acids of optimum concentration, the extracts thus obtained being separately or jointly treated with caustic or the like for the purpose of recovering or cracking out the nitrogen bases thus extracted from the complex sludge mixtures.

The following is a specific method of extracting nitrogenous compounds from the complex sludge mixtures resulting from the treatment of petroleum distillates with heavy metal salts such as zinc chloride. In this particular case, the starting material consisted of sludges derived from treating cracked gasoline fractions with zinc chloride salts. This material was a' black, rather viscous mixture which contained, in addition to the bases, quantities of water, emulsified hydrocarbons, and complex zinc salts. The crude material, for purposes of easier handling was first dissolved in three volumes of kerosene'extract bottoms, and a 200 m1. sample was lixiviated three times with water, 500 ml. of water being employed for each extraction. After each treatment the water layer was separated, and it was found that 60% of the bases contained in the crude material was recovered by the first extraction, 19% by the second and 3% by the third. Therefore, 82% of the nitrogen bases was thus simply and very economically extracted from the sludges. These bases were liberated from the water phase by the addition of caustic, which simultaneously, caused the precipitation of the metal salts.

The residual material, after the above water extractions, was then extracted with 200 m1. of 5% sulphuric acid to recover the free bases and the water insolublecomplex salts still present in the sludges. After separation of the acid solution from the sludges and after treatment with caustic, an additional 11% of the nitrogen bases originally present in the crude material was separated as a supernatant layer. The remaining 7% of nitrogen bases was then extracted from the sludges by a further lixiviation with 500 .ml. of water. As in the preceding cases, the separated water solution was causticized for the liberation of these nitrogen bases.

In another example, 290 ml. of the above described type of sludge obtained from the treat- 4 ment of a cracked gasoline fraction with zinc chloride was water extracted three times, 2 volumes of water being used for each extraction. In this case however the crude material was not diluted and it was found that the phase separation took a somewhat longer period of time, the aqueous layer also containing small quantities of suspended oil. The aqueous extracts thus produced contained the nitrogen bases as the water soluble salts of the general formula of (Base)z-ZnCl2 and (Base-I-ICl)2-ZnCl2. After each extraction the aqueous phase was separated from the residual sludge, and was treated with extract to liberate the nitrogen bases from their water soluble salts.. These nitrogen bases were then removed, and it was found that'the three extractions respectively yielded or. separated 51%, 19% and 11% of the total bases originally present in the sludge. In other words, the three extractions removed 81% of the bases present.

It is thus seen that the above described method of recovering nitrogen bases from complex sludges obtained during the heavy metal salt treatment of petroleum fractions and the like is very simple and economical. This method eliminates or at least considerably decreases the quantity of acid necessary for the extraction of bases. Furthermore, the use of relatively smaller quantities of inorganic acids correspondingly decrease the quantity of caustic (such as sodium hydroxide) necessary for the liberation or cracking out of free nitrogen bases.

Although sodium hydroxide has been mentioned as the caustic for the liberation or cracking out of the nitrogen bases, it is to be understood that other neutralizing agents, such as lime, etc., are within the scope of equivalents.

It is to be further understood that the inven tion is'not to be limited by any specific detail disclosed herein, since many variations obvious to those skilled in the art may be made Within the scope of this invention Thus, when it is not necessary or desirable to extract all of the bases, it is possible to employ only one Water lixiviation. Also, the acid extraction step (which may be realized by using acids other than sulphuric acid) may be eliminated. In such case, the water insoluble base salts and the free bases will be left in the sludge.

The above described process of extracting nitrogen bases is not limited to sludges obtained by treatment of petroleum fractions or the like with zinc chloride, it being understood that acid process applies with equal force to all types of sludges or fractions which contain double salts of the nitrogen bases. Thus, the water extraction process may be employed for the treatment of sludges produced from the treatment of the oil fractions with such salts as mercuric chloride, cadmium chloride, lead chloride and copper chloride. as well as with other halides and sulphates of these and like metals. In fact, the water ex traction process is applicable to the treatment of products in which water soluble inorganic salts are combined with the nitrogen base to form a complex containing two molecules of nitrogen base per molecule of the inorganic salts, or in which these organic bases are combined with the hydrochlorides of these inorganic salts. Also, as stated, the raw stock to be extracted according to the present process may be produced from other sources, as for example, from shale oils, coal tars and products obtained by pyrolysis of certain organic substances, such as cottonseed meal.

I claim:

1. A process for extracting and recovering organic nitrogen bases fromcrude materials resulting from the treatment of petroleum, shale oil, coal tar and products obtained by the pyrolysis of cottonseed meal with halides of a metal selected from the class consisting of zinc, cadmium, mercury, lead and copper, which crude material contains impurities and complex metal salts of organic nitrogen bases, said process comprising subjecting said crude material to a plurality of extractions with water to dissolve the water soluble metal-base salts, separating the aqueous phase containing the water soluble metal-base salts after each of said extractions, contacting the water insoluble crude material, remaining after the water extraction, with an inorganic acid to dissolve the free nitrogen bases and the water insoluble metal-base salts, separating the acid phase, and introducing an alkali therein to liberate the nitrogen bases dissolved in said acid phase.

2. A process for recovering nitrogen bases from es resulting from the treatment of petroleum oils with zinc chloride, said sludges conan inorganic acid solution to dissolve therefrom the free nitrogen bases and the water insoluble complex salts, separating the acidic phase from the insoluble sludge, and causticizing said acidic phase to liberate therefrom the nitrogen bases dissolved therein.

GEORGE RYDER LAKE. 

